Postharvest Diseases of Cherries
Some of the same diseases attack pears, apples and cherries, and these have been described under the apple and pear section. Postharvest diseases unique to cherries are described below. Many diseases of cherries are significantly more serious during seasons in which rain-cracking occurs.
Cladosporium Rot (Cladosporium
This fungus is widespread in orchards but only enters the fruit through breaks in the skin. Careful handling, removal of damaged fruit and rapid cooling are the only effective management tools for the decay.
Rhizopus Rot (Rhizopus spp.)
This is one of the most serious postharvest diseases of cherries. Infection usually occurs after harvest and enters the fruit at cuts, cracks or bruises. The fungus will not develop below 45°F and can be controlled with effective temperature management, holding the cherries as close to 32°F as possible.
Apply mildew fungicides according to recommendations.
Shield harvested fruit from sun and heat as much as possible.· Minimize exposure of picked fruit to dead Plant material (leaves, twigs, sticks, grass, etc.) and dust. Place picked cherries in clean, dry lugs or bins.
Hydrocooling cherries removes field heat, contributes to longer shelf life and provides the first opportunity to clean the fruit and remove fungal spores that can cause infection and decay in storage.
Hydrocool cherry varieties which are not damaged by hydrocooling (e.g., Bings) as soon after harvest as practical.
When outside hydrocoolers are used, 2.0 to 3.0 ppm chlorine dioxide combined with a low foaming, ethoxylated linear alcohol surfactant (and antifoam agent if necessary) should be used. This maintains green stem color during subsequent storage and will clean and partially disinfect the fruit of field-borne fungal spores. Chlorine dioxide treatment should be followed by potable water rinse. When hydrocoolers are located indoors, use 100 ppm free chlorine with a surfactant instead of chlorine dioxide. The pH of hydrocooler water after addition of hypochlorite should be 7.0 to 8.0 for maximum antimicrobial activity. Free chlorine levels should be monitored regularly, hourly if possible.
For Lambert and Rainier cherries, treat with a chlorine dioxide or chlorine/surfactant dip or drench followed by fresh water rinse. An automated system for monitoring and control of free chlorine levels directly or by pH is highly recommended. This will minimize chlorine level fluctuations over time and will increase the effectiveness of the chlorine treatment.
After hydrocooling or chlorine immersion treatment, store fruit as close to 32°F as possible until run on packing line. Flume waters should be maintained at 50 ppm free chlorine, pH 7.0 to 8.0.
Fruit should receive potable water rinse after any chlorine or oxychlorine treatment.
Minimize (preferably eliminate) soil adhering to bin skids, as this can be a source of Penicillium, Mucor and Rhizopus spores.
The importance of good sanitation cannot be overemphasized. Fruit otherwise handled properly to prevent decay can become reinfected with fungal spores from packing line equipment if the equipment is not kept clean.
Remove all damaged, crushed or otherwise extraneous fruit from packinghouse floors, belts, pulleys and any surface that comes in contact with fruit.
Periodically clean all equipment in contact with fruit with a detergent, then sanitize with a surface sanitizer approved for food handling surfaces.
Thoroughly cull all split, crushed or otherwise damaged fruit at the earliest possible step dining cherry processing.
Do not store culled fruit in the same room with processed fruit.
See chemical control section for labelled fungicides, rates and methods of application.
Treat fruit as soon after harvest as practical. Follow recommended practices and precautions for all fungicides.
Mike Willett(1), Gene Kupferman(2), Rodney Roberts(3), Robert Spotts(4), Dave Sugar(5), Gary Apel(6), Hugh W. Ewart and Bill Bryant (7)
(1)WSU Cooperative Extension Agent, Yakima, WA; (2)Postharvest Specialist, WSU TFREC, Wenatchee, WA; (3)USDA Pland Pathologist, Tree Fruit Research Lab, Wenatchee, WA; (4)OSU Plant Pathologist, Mid-Columbia Research and Extension Center, Hood River, OR; (5)OSU Plant Pathologist, Southern Oregon Experiment Station, Medford, OR; (6)Michelsen Packaging Company, Yakima, WA; (7)Northwest Horticultural Council, Yakima, WA
Post Harvest Pomology Newsletter, 7(3): 12-14